iCloud email aliases in Apple Mail are not showing up in iCloud.com

I have 5 aliases associated with my iCloud account. I am a long-time Mac.com/MobileMe user, hence the large amount of aliases. Some of them I haven't used in years. But, they are all listed in Apple Mail as possible sender accounts when I compose a new email message. I want to delete 1 of these aliases) (let's call this "alias5". So I signed into iCloud.com, but only 3 of the 5 aliases are listed ("alias4" and "alias5"). AND, when I try sending email from Apple Mail from either of these 2 accounts, only 1 of them is functioning ("alias4"). I am unable to send mail from the other one ("alias5").

Question: 1) How do I delete the non-functioning one ("alias5") from my list of addresses in Apple Mail, and

2) What can I do to get the fully-functioning alias ("alias4") to show up in iCloud.com so I have control over options and preferences?

Thanks!